The synergistic integration of elastic porous material with self-powered sensing capabilities holds immense promise for smart wearable devices. However, the intrinsic contradiction between elasticity and strength has hindered the mechanical performance of elastic porous materials. This research reports a diffusion-driven layer-by-layer assembly strategy to enhance the mechanical strength of elastic porous materials. As a prerequisite, the anisotropic layered structure of natural materials is leveraged to endow the porous material with fundamental elasticity. Subsequently, vacuum and chemically-assisted enhanced solvent diffusion are sequentially employed to assemble conductive and elastic layers on cellulose from the inside out. This endows the triboelectric material (TM) with exceptional mechanical properties (elastic strain range of 0–80%, compressive strength reaching 4.55 MPa). Utilizing the TM as a sensing material, a self-powered sensor with a response time of 48 ms and a sensitivity of 0.57 kPa−1 is constructed. Moreover, the application of the sensor in a smart wearable helmet is demonstrated, enabling remote monitoring and traceability of head impact events. This research has overcome the incompatibility between the high strength and elasticity of porous materials and offers promising avenues for their utilization in smart wearable devices.